Infections caused by C. trachomatis primarily localize to ocular and genital tract mucosae where they commonly produce asymptomatic infections or acute self-limiting infections such as uncomplicated conjunctivitis, urethritis, or cervicitis. However, these infections occasionally progress to chronic infections that provoke severe inflammatory responses which may lead to blindness or infertility. C. trachomatis is the leading cause of sexually transmitted infection in the United States and Europe. In women, chlamydial infections of the lower genital tract can ascend to infect the fallopian tubes, produce chronic salpingitis, and cause infertility or ectopic pregnancy by tubal blockage. We previously identified the chlamydia 60kD heat shock protein (HSP60) as an antigen that elicits a local (mucosal) delayed hypersensitivity (DTH) response. We proposed that this immune response is pathogenetic and contributes to the development of the severe sequelae (blindness and infertility) that often follow chlamydial infection. The major focus of this project is to characterize the antigenic properties of the chlamydia HSP60, and to identify the immune responses elicited by this antigen that contribute to the pathogenesis of disease. This past year we have focused on preparing reagents that will allow us to evaluate the immune response to this antigen in detail. Anti- chlamydia HSP60 monoclonal antibodies were prepared. Eleven mAbs were obtained and their reactivities defined. Five mAbs were chlamydia specific and six cross-reacted with HSP60s from other gram-negative bacteria. One chlamydial specific mAb was useful for the affinity purification of HSP60, and all reacted with HSP60 polypeptides representing the entire primary amino acid sequence of the protein. These recombinant, truncated polypeptides will be useful for localizing the antibody and T cell domains of the HSP60 molecule. We are also utilizing in vitro models of chlamydial persistence to evaluate the possibility that cells persistently infected with chlamydiae act as antigenic depots for stimulation of chronic inflammatory responses. Interestingly, persistently infected cells contain elevated levels of chlamydia HSP60 compared to other chlamydia antigens, and preliminary evidence indicates that the chlamydia HSP60 is released from such infected cells. In the upcoming year we will define the T cell immune response to the chlamydial HSP60 and continue to evaluate the possibility that persistently infected cells function as depots of "deleterious" antigen.